No NVENC capable devices found - nvenc

Question

I met a weird question.I have been using FFmpeg's NVENC to encode video .It is strange that I can use h264_nvenc smoothly without problem,but when I replace h264_nvenc with hevc_nvenc，I got the problem "No NVENC capable devices found".The FFmpeg version I am using is 3.2,and I use command line to encode with hevc_nvenc，it works ok.My code is here:
#include "stdafx.h"
int flush_encoder(AVFormatContext *fmt_ctx, unsigned int stream_index)
{
int ret;
int got_frame;
AVPacket enc_pkt;
if (!(fmt_ctx->streams[stream_index]->codec->codec->capabilities &
CODEC_CAP_DELAY))
return 0;
while (1) {
printf("Flushing stream #%u encoder\n", stream_index);
//ret = encode_write_frame(NULL, stream_index, &got_frame);
enc_pkt.data = NULL;
enc_pkt.size = 0;
av_init_packet(&enc_pkt);
ret = avcodec_encode_video2(fmt_ctx->streams[stream_index]->codec, &enc_pkt,
NULL, &got_frame);
av_frame_free(NULL);
if (ret < 0)
break;
if (!got_frame){
ret = 0;
break;
}
printf("Succeed to encode 1 frame! 编码成功1帧！\n");
/* mux encoded frame */
ret = av_write_frame(fmt_ctx, &enc_pkt);
if (ret < 0)
break;
}
return ret;
}
int main(int argc, char* argv[])
{
AVFormatContext* pFormatCtx;
AVOutputFormat* fmt;
AVStream* video_st;
AVCodecContext* pCodecCtx;
AVCodec* pCodec;
uint8_t* picture_buf;
AVFrame* picture;
int size;
FILE *in_file = fopen("test_yuv420p_320x180.yuv", "rb"); //Input YUV data 视频YUV源文件
int in_w = 320, in_h = 180;//宽高
int framenum = 100;
const char* out_file = "ds.hevc";
av_register_all();
//Method1 方法1.组合使用几个函数
pFormatCtx = avformat_alloc_context();
//Guess Format 猜格式
fmt = av_guess_format(NULL, out_file, NULL);
pFormatCtx->oformat = fmt;
//Method 2 方法2.更加自动化一些
//avformat_alloc_output_context2(&pFormatCtx, NULL, NULL, out_file);
//fmt = pFormatCtx->oformat;
//Output Format 注意输出路径
if (avio_open(&pFormatCtx->pb, out_file, AVIO_FLAG_READ_WRITE) < 0)
{
printf("Failed to open output file! 输出文件打开失败");
return -1;
}
video_st = avformat_new_stream(pFormatCtx, 0);
video_st->time_base.num = 1;
video_st->time_base.den = 25;
if (video_st == NULL)
{
return -1;
}
//Param that must set
pCodecCtx = video_st->codec;
pCodecCtx->codec_id =AV_CODEC_ID_HEVC;
//pCodecCtx->codec_id = fmt->video_codec;
pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
pCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
pCodecCtx->width = in_w;
pCodecCtx->height = in_h;
pCodecCtx->time_base.num = 1;
pCodecCtx->time_base.den = 25;
pCodecCtx->bit_rate = 400000;
pCodecCtx->gop_size = 12;
//H264
//pCodecCtx->me_range = 16;
//pCodecCtx->max_qdiff = 4;
//pCodecCtx->qcompress = 0.6;
pCodecCtx->qmin = 10;
pCodecCtx->qmax = 51;
//Optional Param
pCodecCtx->max_b_frames = 3;
// Set Option
AVDictionary *param = 0;
//H.264
if (pCodecCtx->codec_id == AV_CODEC_ID_H264) {
av_dict_set(&param, "preset", "slow", 0);
av_dict_set(&param, "tune", "zerolatency", 0);
}
//H.265
if (pCodecCtx->codec_id == AV_CODEC_ID_H265){
av_dict_set(&param, "x265-params", "qp=20", 0);
av_dict_set(&param, "preset", "default", 0);
av_dict_set(&param, "tune", "zero-latency", 0);
}
//Dump Information 输出格式信息
av_dump_format(pFormatCtx, 0, out_file, 1);
//pCodec = avcodec_find_encoder(pCodecCtx->codec_id);
pCodec = avcodec_find_encoder_by_name("hevc_nvenc");
if (!pCodec){
printf("Can not find encoder! 没有找到合适的编码器！\n");
return -1;
}
if (avcodec_open2(pCodecCtx, pCodec, &param) < 0){
printf("Failed to open encoder! 编码器打开失败！\n");
return -1;
}
picture = av_frame_alloc();
size = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
picture_buf = (uint8_t *)av_malloc(size);
avpicture_fill((AVPicture *)picture, picture_buf, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
//Write File Header 写文件头
avformat_write_header(pFormatCtx, NULL);
AVPacket pkt;
int y_size = pCodecCtx->width * pCodecCtx->height;
av_new_packet(&pkt, y_size * 3);
for (int i = 0; i<framenum; i++){
//Read YUV 读入YUV
if (fread(picture_buf, 1, y_size * 3 / 2, in_file) < 0){
printf("Failed to read YUV data! 文件读取错误\n");
return -1;
}
else if (feof(in_file)){
break;
}
picture->data[0] = picture_buf; // 亮度Y
picture->data[1] = picture_buf + y_size; // U
picture->data[2] = picture_buf + y_size * 5 / 4; // V
//PTS
picture->pts = i;
picture->format = pCodecCtx->pix_fmt;
picture->width = in_w;
picture->height = in_h;
int got_picture = 0;
//Encode 编码
int ret = avcodec_encode_video2(pCodecCtx, &pkt, picture, &got_picture);
if (ret < 0){
printf("Failed to encode! 编码错误！\n");
return -1;
}
if (got_picture == 1){
printf("Succeed to encode 1 frame! 编码成功1帧！\n");
pkt.stream_index = video_st->index;
ret = av_write_frame(pFormatCtx, &pkt);
av_free_packet(&pkt);
}
}
//Flush Encoder
int ret = flush_encoder(pFormatCtx, 0);
if (ret < 0) {
printf("Flushing encoder failed\n");
return -1;
}
//Write file trailer 写文件尾
av_write_trailer(pFormatCtx);
//Clean 清理
if (video_st){
avcodec_close(video_st->codec);
av_free(picture);
av_free(picture_buf);
}
avio_close(pFormatCtx->pb);
avformat_free_context(pFormatCtx);
fclose(in_file);
system("pause");
return 0;
}
Help!!!!

Answer 1

after a few days of strugglling,once again I try anwser the question myself.The key point is ,when encoding with hevc_nvenc，you must set pCodecCtx->max_b_frames = 0;(at least for version 3.2 of ffmpeg).